Since the development of synthetic aperture, attempts have been made to reduce the size, weight, power consumption, and cost of these systems. Basically, a target crossing a radar beam produces a chirp signal at the output of a detector. The chirp signal is then processed electronically in a matched filter in real time or is recorded and then reproduced at a later time in an optical matched filter. The real time operation of the electronic processor is obtained at the expense of large size, weight, and power consumption of the processor while the small size, weight, and power consumption of the optical processor is obtained at the expense of an annoying delay of obtaining images. Examples of conventional synthetic aperture can be found in the paper by L. Cutrona et al., "On the Application of Coherent Optical Processing Techniques to Synthetic Aperture" appearing in the August, 1966 issue of Proc. IEEE, and in the paper by W. Brown and L. Porcello, "An Introduction to Synthetic Aperture Radar" appearing in the September, 1969 issue of IEEE Spectrum. While these systems first record detected signals and then reproduce images in a time consuming two step process, my U.S. Pat. No. 3,691,557 System for Identifying Objects Using an Encoding Array for each Object, U.S. Pat. No. 3,790,939 Real Time Synthetic Radar, U.S. Pat. No. 3,798,644 Vector Velocity System, and U.S. Pat. No. 3,858,203 Synthetic Radiometer and System for Identifying Objects are examples of systems which process their signals electronically in real time.
While all the known apparatus and methods of the prior art have the ability to form synthetic apertures, they have significant inherent disadvantages. For example, systems using optical processing while significantly reducing the size, weight, and power consumption of processors and increasing the data capacity for two dimensional image do so at the expense of a two step recording and then reproducing cycle which often is time consuming in many applications. On the other hand, systems using electronic processing while operating in real time do so at the expense of having large size, weight and power consumption of their signal processors and having a reduced data capacity. Because of these disadvantages, the conventional synthetic aperture has found limited use, mainly in military surveillance, reconnaisance, and ground mapping applications and has found no commercial application whatsoever. It is desired to provide a synthetic aperture apparatus and method that overcomes these disadvantages so that the benefits of synthetic aperture will have a widespread and commercial use. More specifically, it is desirable to provide a synthetic aperture apparatus and method that has a real time operation yet has a small size, weight, power consumption, cost and high data capacity, i.e., combining the best features of the prior art systems while eliminating their disadvantages.
Charge transfer image sensors have been developed using a variety of technologies including solid state (SS), charge coupled devices (CCD), charge injection devices (CID) and bucket brigade devices (BBD). These devices are used to view an object scene or picture and to convert light intensity from the object scene into electrical signals. Transmitted to a remote location, these signals can reproduce an image of the real object scene with high resolution. Linear image sensors consist of a single row of photoelements and, therefore, image a single line of optical information. In a frame, i.e., a number of lines, of optical information is desired either the image or the device must be moved from line to line to obtain the information. Linear image sensors are used in facsimile, slow scan TV, optical character recognition or label reading systems. They also find application in monitoring industrial processors where the processed items are inspected as they pass the linear sensor. Area image sensors, on the other hand, find applications in the imaging of two dimensional object scenes, usually under low light level illuminations and providing compact, light-weight, low power consuming stable operating long life camera systems. Area imagers consist of a rectangular array of photoelements. Like the linear devices there are different methods of reading out the stored video information obtained by the photoelements, for example the information in the photoelements can be read out serially, in serial-parallel and in parallel formats. Image sensors, their architecture and methods of operation have been described in a number of publications including the article by Amelio "Charge Coupled Devices" appearing in the May, 1974 issue of Scientific American, in the article by Solomon "CCD Image Sensors" appearing in Paper 2 presented at the IEEE Western Electronic Show and Convention (WESCON) Los Angeles, Sept. 10-13, 1974, in the article "A new imaging technology grabs hold: Charge Transfer Devices" appearing in the Mar. 15, 1974 issue of Electronics Design and in the article by Deliduka "Enormous Bucket-Brigade Optical Scanner Achieves High Efficiency" appearing in the February, 1976 issue of Computer Design. Commercially available image sensors and associated equipment are shown in the brochure of Reticon Corp., entitled Product Summary Solid State Image Sensors and Systems, published in 1973.
Present image sensors work splendidly when the object or view scene is stationary relative to the sensor and even work in a limited respect as the object scene moves across the sensor's field of view at relatively low speed. However, the capability of present image sensors quickly degrades at speeds beginning to approach the modest value of a small fraction of one kilometer per hour. Thus, while the known apparatus and methods of the present image sensors have the ability to form images at stationary and very low speeds they fail at high image speeds. Moreover, there are not known image sensors for generating a synthetic aperture must less than for generating a synthetic aperture using noncoherent as well as coherent radiations, or for using clock means for signal processing, or for changing the range focusing of the object scene, or for operating at high rates of motion of the object scene, or of operating at other than optical frequencies.
Therefore, it is an object of this invention to provide apparatus and method for generating a synthetic aperture using image scanners.
It is also an object of this invention to provide apparatus and method for generating a synthetic aperture using coherent or non coherent radiations from objects.
It is another object of this invention to provide apparatus and method for processing signals using an image sensor.
It is another object of this invention to provide apparatus and method for an imager which is capable of changing the range focusing of its object scene.
It is another object of this invention to provide apparatus and method for an imager which is capable of operating at acoustical, microwave or optical frequencies.
It is another object of this invention to provide apparatus and method for viewing images using image scanners.
It is another object of this invention to provide apparatus and method for detecting and correlating desired images using image scanners.
It is yet another object of this invention to provide apparatus and method for reading coded labels.